The present invention relates to a system and method for fabrication of film(s) onto a variety of surfaces with semiconductor materials, metals, or insulators for various applications including electronics. More particularly, the invention pertains to methods for making films for electrochemical cells and other applications.
Numerous coating processes like electroless chemical, chemical vapor, and physical vapor depositions are commonly employed in industrial applications. Physical vapor deposition is commonly used in semiconductor manufacturing applications, often employing expensive vacuum techniques in order to sustain a relatively high film growth rate. Many such processes, while performed at high temperatures (e.g., greater than 300.degree. C.), are non-equilibrium, often resulting in non-stoichiometric proportions. Also, due to the nature of the deposition processes, the deposited films often include relatively high defect densities. In the case of semiconducting devices, such high defect levels can limit electrical performance characteristics. In semiconductor device fabrication wherein p-n junctions are formed in a partial vacuum by depositing one film over a second film or a substrate of different conductivity type, the conventional evaporative and sputtering techniques may provide unsatisfactory film qualities. As an alternative, relatively more expensive techniques such as Chemical Vapor Deposition (CVD), Molecular Beam Epitaxy (MBE), pulsed laser deposition, and atomic layer epitaxy, are useful, especially with formation of III-V compound semiconductor materials, but satisfactory deposition processes have not been available for fabrication of thin film II-VI compound semiconductor materials. An example of a process is described in U.S. Pat. No. 8,225,744, in the name of Oladeji, and issued on Jul. 24, 2012, which is incorporated by reference herein.
The above are expensive vacuum techniques; and the process involved is based mostly on the intermixing of elements constituting the material and subjecting the mixture to high temperature to form the compound. Unfortunately each of the various elemental particles does not have the same surrounding. Hence, small isolated areas will have the right material composition after anneal leading to film with non-uniform stoichiometry. Thus, the process may be good for small area deposition but poor for large area deposition needed for high yield manufacturing.
From the above, it is seen that techniques for depositing high quality films are desirable.